1. Field of the Invention
This invention relates to a pneumatically actuated switching device and more particularly to an improved construction and arrangement of parts to form a pneumatic bulb for delivering a quantity of pressurized air to a site remote from the bulb for triggering a switching device to produce an electrical signal in a nurse call system.
2. Description of the Prior Art
A pneumatically actuated bulb device is known in the art for a patient actuating a nurse call system and an example of such a device is disclosed in my prior art U.S. Pat. No. 3,823,285. The pneumatic bulb provides a source of pressurized air to operate an electrical switching circuit that is well suited for use in environments where it is undesirable to use a conventional electrical switch. The possibility exists of a catastrophic explosion when a conventual switching circuit operates in an atmosphere containing a high concentration of a potentially explosive gas. Such an atmosphere commonly occurs in hospital rooms due to a patient's use of oxygen. A patient actuated call system is not only commonly used in hospital rooms but also in other health care facilities where there is a need or desire by some person for help, particularly, when a patient is in a weakened or disabled condition. Most hospitals and health care institutions today have signalling systems by which in each patient area a patient may initiate a signal that is received of a station or at an allocated substation within a larger area to summon assistance. Typically, for example, in a hospital a select group of patient areas is serviced by a given nurse station where calls for assistance by patients are taken. Most patient areas must accommodate the use of oxygen even if it is only on an emergency base whereby electrical switches commonly used in other industries can not be utilized. The pneumatically operated switch disclosed in my aforesaid U.S. Pat. No. 3,823,285 provides an entirely satisfactory solution to the need for a pneumatically activated switching 10 device which can operate in a very reliable fashion in hostile environments. This switching device successfully operates in atmospheres containing a high concentration of oxygen that could otherwise cause combustion. A need, however, exists for a pneumatic bulb construction that is better suited for the environment of use particularly in a patient environment where patients can assume that the pneumatic device will remain in place without random or uncontrolled movement. For example, a pneumatic bulb having a spherical configuration or a configuration having hemispherically end parts adjoined with a cylindrical mid-section can not be relied upon to remain in a fixed or desired location on a patient's mattress so that the patient can utilize the bulb to summon help. The rounded configuration of the bulb and patient movement all contributed to the fact that the bulb will move randomly in an uncontrolled manner. Moreover, a need exists for a pneumatic bulb construction which will allow a pressurized air supply to be developed in a reliable manner requiring minimal effort on behalf of the operator of the pneumatic bulb.
Examples of other known nurse call systems can be found in U.S. Pat. Nos. 4,702,443; 4,484,367; 4,298,863; and 3,781,843. In U.S. Pat. No. 4,702,443, a cord holding device is disclosed wherein a belt fastener is used to hold a base onto a mattress so that the base can in turn receive a cord holding member. The cord holding member supports a cord to allow limited movement of the cord the end of which carries a push button electric switch. In U.S. Pat. No. 4,484,367, a side rail of a patients bed is wrapped with a flexible sheet having a pocket in one side of the sheet for receiving an electronic push button device serving as a call device for summoning a nurse. U.S. Pat. No. 4,298,863 discloses a patient call system in which a patient operated transducer is mounted on a patients face or a portion of the body. The transducer is interconnected by pneumatic tubing to an pneumatically actuated switch that is part of an electronic monitoring system. U.S. Pat. No. 3,781,843 discloses a bed guard system in which the upper rail surfaces of patient restraining rails at opposite sides of a bed are fitted with a detector. Each detector is formed with an elongated rail engaging pocket shape to fit on the rail surface and an overlying elongated internal cavity extending generally the length of the rail. In internal cavity forms a site for a fluid material which can be pressurized by an applied pressure to the top surface of the rail covering.